The Year in Science: Plants 1997

An Ancient Convenience

Cloning may be big news in the animal kingdom, but to plants it’s a big yawn. They’ve been reproducing by cloning since day one. The more recent trend in the vegetable set is sex—in particular, using distinct sperm and egg cells. But a tiny fossil described in Nature last January suggests that trend, too, has been around for quite a while.

Paleontologist Raimund Feist of the University of Montpellier II chanced upon the 405-million-year-old fossil in the Montagne Noire mountains in southwestern France. Not a plant man himself, Feist nevertheless recognized the one-millimeter-wide fossil as a possible charophyte—a type of green alga that lives in rivers and lakes and that just happens to be the area of expertise of his wife, Monique, a paleobotanist at the same university. He asked me, ‘Do you think it might be a charophyte?’ And I said, ‘Yes! Ooh, amazing,’ she recalls. And it became evident that it was the oldest bisexual plant yet discovered.

In fact, it is the oldest plant yet found with distinct male and female sex organs—earlier sexual plants exchanged identical gametes—and like modern flowers, it is bisexual in that it carries its male antheridia and female oogonia on the same structure. The fossil charophyte shares a common ancestor with land plants. Botanists have long debated whether the earliest sexually reproducing plants were unisexual, bearing either female or male sex organs, or bisexual. The French fossil offers support for the latter hypothesis.